In this type of internal combustion engine, there are suggested various technologies of reducing unburned hydrocarbon (hereinafter referred to as “HC”, as occasion demands) or the like to thereby prevent the deterioration of exhaust emissions. For example, in a patent document 1, there is suggested a technology of delaying the valve open timing of an exhaust valve so that a combustion gas in a cylinder stays longer than usual, at the cold start of the engine. In a patent document 2, there is suggested a technology of setting the exhaust valve in an almost fully close status, at the start and the warm-up operation of the engine. In a patent document 3, there is suggested a technology of setting the valve overlap, in which both the intake valve and the exhaust valve are close, to be substantially equal at the start of the engine and the subsequent idling, and of setting the overlap center to locate on the more advanced angle side as the temperature of the engine drop. In a patent document 4, there is suggested a technology of advancing the angle of the exhaust valve after HC is reduced by increasing the valve overlap and by bringing an exhaust gas back into the cylinder and burning it, at the start of the engine. In a patent document 5, there is suggested a technology of increasing a burned gas ratio in filled gases and of burning HC again by opening the exhaust valve on the basis of the operating condition of the engine.    Patent document 1: Japanese Patent Application Laid Open NO. 2005-147015    Patent document 2: Japanese Patent Application Laid Open NO. 2001-59428    Patent document 3: Japanese Patent Application Laid Open NO. 2004-176680    Patent document 4: Japanese Patent Application Laid Open NO. 2002-206436    Patent document 5: Japanese Patent Application Laid Open NO. Hei 5-86908